Ok, I havn't read all of it, but 3.0D (stock) vs. 4.4i (pre-facelift, stock) I can tell you that 4.4i is faster in acc. but I didn't do it, guys who compared told me. But then again I do go faster then all pre-facelift 4.4i-s that I tried to compete with, and mine is also stock. I also tried with facelifted 4.4i and we got same result until 4th gear, on 4th he started going faster, but my sunroof was open(that does do damage on aerodynamics) what else? no way that 3.0D chipped will do 4.8is. Plus Gotta love the sound. efficency does do a job, but if you don't care, go for V8. I had opportunity for switching my car to 4.6is, but I decided to wait and go for 4.8is in winter. that IS vs. nonIS difference metters to me. so decide on your own. if you want car which pulls harder, V8 is way to go. and NM difference will do, but for start, as soon as you redline it, Horsepower wins.